9 12 10 11You dont have to flee any longer Body’s Digest
STRUCTURE AND FUNCTION The cerebral cortex is a thin layer of secondary, tertiary. (1) (399)gray matter made up of neuron dendritesand cell bodies that compose the surface Somatic motor pathways in the CNS: For the cerebral cortex to per-of the cerebrum. Consists of 2 halves a form its motor functions, impulsesright and left half. It controls sensory, are conducted from its motor areasmotor, consciousness, language, emotions to skeletal muscles by somatic mo-and memory. (1) (393) tor pathways. Consists of motor neu-Somatic Sensory pathways in the CNS: rons that conduct impulses from theFor the cerebral cortex to perform its CNS to skeletal muscles.(1) (400)sensory functions, impulses must firstbe conducted to the sensory pathways.Sensory paths to the cerebral cortexare crossed. There are three main poolsof sensory neurons there are primary,
8 Make it work sista and fight!With the Sensory and motor pathways you are now fully aware of yourbrains messaging throughout nerve impulses and the power with in your-self. You’re practically a superhero!
Peripheral Nervous Sys. There are thirty-one pairs of spinal root ganglion, or spinal ganglion.nerves that are connected to the spi- (1)nal cord, although they don’t have Plexuses:special names they are numbered ac-cording to the level of the vertebral The ventral rami of most spinalcolumn at which they emerge from nerves subdivide to form complexthe spinal cavity. (1) networks called plexuses. There are four major types of plexuses,Structure of the Spinal Nerves: and they are the cervical plexus,The structure of the spinal nerves the brachial plexus, the lumbaris separated into two sections, which plexus and the sacral plexus. (1)are attached to the spinal cord in Cervical Plexus is found deep with-terms of roots. These roots are the in the neck, the parts suppliedventral and dorsal. The dorsal root with this are the sensory to theof each spinal nerve is easily recog- back of the head, front of the neck,nized by a swelling called the dorsal and upper part of the shoulder; mo
Peripheral Nervous Sys. tor to numerous neck muscles. (1) Dermatomes & Myotomes:Brachial Plexus is found deep Dermatomes- regions of skin surface ar-within the shoulder. Lumbar Plex- ea supplied by afferent (sensory) fibers ofus, which is formed by the inter- a given spinal nerve. (1)mingling of fibers from first fourlumbar nerves. This network of Myotomes- skeletal muscles supplied bynerves is located in the lumbar efferent (motor) fibers of a given spinal nerve. (1)region of the back near the soasmuscle. Sacral Plexus are the fi- Cranial Nerves:bers from the fourth and fifthlumbar nerves and the first four There are twelve pairs of cranial nerves that connect to the brain, mostly to thesacral nerves. It lies in the pelvic brainstem. They are also made up ofcavity on the anterior surface of bundles of axons, which are the mixedthe piriformis muscle. cranial nerve where axons of sensory and
Peripheral Nervous Sys. motor neurons. Sensory cranial 10) Vagus Nerve nerve- axons of sensory neu- 11) Accessory Nerve rons only. Motor cranial nerve- 12) Hypoglossal Nerve mainly axons of motor neurons Afferent & Efferent Nerves: and a small number of sensory fibers (proprioceptors). There are two functional divi-1) Olfactory Nerve sions of the peripheral nervous2) Optic Nerve system which are the afferent3) Oculomotor Nerve (sensory) division and the effer-4) Trochlear Nerve ent (motor) division. The effer-5) Trigeminal Nerve ent division is divided further6) Abducens Nerve into the somatic motor nervous7) Facial Nerve system and the efferent portions8) Vestibulocochlear Nerve of the autonomic nervous sys-9) Glossopharyngeal Nerve tem. (1)
Peripheral Nervous Sys. Autonomic Nervous System: 1) Preganglionic neuron- conducts impulses from the central nervousStructure:: each pathway is up system to an autonomic ganglion.of autonomic nerves, ganglia, 2) Postganglionic neuron- efferentand plexuses, which are made of neuron with which a preganglion-efferent autonomic neurons. All ic neuron synapses with autonom-autonomic neurons function in ic ganglionthe reflex arcs. Efferent auto- Function:: the autonomic nervous sys-nomic regulation ultimately de- tem functions to regulate visceralpends on the feedback from sen- effectors in ways that tend to main-sory receptors. Relay of two ef- tain or quickly restore homeostasis.ferent autonomic neurons con- Sympathetic and Parasympatheticducts information from central divisions are tonically active, oftennervous system to autonomic ef- exerting antagonistic influences onfectors: visceral effectors.
Peripheral Nervous Sys. Doubly innervated effectors con- maintain normal tone of the smoothtinually receive both sympathet- muscle in blood vessel walls. The ma-ic and parasympathetic impuls- jor function of this system is that ites, and the summation of the serves as an “emergency” system-two determine the controlling the “fight-or-flight” reaction. (1)effect. Parasympathetic Nervous System:Sympathetic Nervous System: The purpose of the parasympatheticThe purpose of the sympathetic nervous system is the dominant con-nervous system is that under troller of most autonomic effectorsresting conditions, the sympa- most of the time. This includes Ace-thetic division can act to main- tylcholine which slows the heartbeattain the normal functioning of and acts to promote digestion anddoubly innervated autonomic ef- elimination. (1)fectors. As a result the sympa-thetic impulses function to
The Brainstem Three divisions of the brain The pons, like the medulla, is alsomake up the brainstem, the me- composed of white matter and retic-dulla oblongata, the pons, and ular formation. Fibers that runthe midbrain. (1) transversely across the pons andThe medulla oblongata is the through the middle cerebellar pe-part of the brain that attaches duncles into the cerebellum make upto the spinal cord, it is about an the external white matter of theinch in length and is separated pons and give it its arching appear-from the pons above by a hori- ance. (1)zontal groove. It is composed ofwhite matter (projection tracts)and a network called the reticu-lar formation. In this reticularformation there are various nu-clei, or clusters of neuron cellbodies. (1) 8
The Cerebellum The midbrain lies below the The cerebellum is the second larg-pons and above the cerebrum. est part of the brain. A transverseBoth white matter and reticular fissure separates the cerebrum fromformation compose the mid- the cerebellum. The cerebellum isbrain. Extending divergently full of white matter much like thethrough it are two ropelike cerebrum, it also has sulci and gyrimasses of white matter named along its surface. The cerebellum iscerebral peduncles. Tracts in composed of two larger lateralthe peduncles conduct impulses masses the cerebral hemisphere andbetween the midbrain and cere- the Vermis. (1)brum. (1) The internal white matter of theThe function of the brainstem cerebellum is composed of someis similar to the spinal cord. It short and some long tracts. Theperforms sensory, motor and re- shorter tracts conduct impulsesflex functions from neuron cell bodies located in
The Cerebellum the cerebellar cortex to neurons -tate nuclei, one of which lies in eachwhose dendrites and cell bodies hemisphere. Tracts connect thesecompose nuclei located in the nuclei with the thalamus and withinterior of the cerebellum. The motor areas of cerebral cortex. Bylonger tracts conduct impulses means of these tracts cerebellar im-to and from the cerebellum. fi- pulses are able to influence the mo-bers of the longer tracts con- tor cortex and vice versa. (1)duct impulses to and from thecerebellum. Fibers of the longertracts enter or leave the cere-bellum by way of its three pairsof peduncles, inferior cerebellar 8peduncles, middle cerebellar pe-duncles, and superior cerebellarpeduncles. An important pair ofcerebellar nuclei are the den-
The Diencephalon The functions of the cerebel- matter made up of many nuclei.;twolum all have to do with the con- in which are the geniculate bodies,trol of skeletal muscles. The located in the posterior region ofcerebellum acts with the cere- each lateral mass. The geniculatebral cortex to produce skilled bodies play a role in processing audi-movements by coordinating the tory and visual input. Large numbersactivities of groups of muscles. of axons conduct impulses into theThe cerebellum also helps to thalamus from all parts of the brain.control posture and maintain These axons terminate the thalamicbalance. (1) nuclei, where they synapse with neu- rons whose axons conduct impulsesThe Diencephalon is made up of out of the thalamus to all areas ofseveral structures. The two the cerebral cortex. Thus the thala-main structures are the thala- mus is a relay station for sensory im-mus and hypothalamus. (1) pulses on their way to the cerebral cortex. (1)The thalamus is a mass of gray
The Diencephalon vival and the enjoyment of life. ItThe thalamus’ functions are functions as a link between the mindtaking impulses from appropri- and the body. And also links to theate receptors and produce a nervous and endocrine system. Theconscious recognition of less hypothalamus serves as a regulatorcritical sensations of pain like and coordinator of autonomic activi-temperature and touch. Plays ties and provides a crucial role in thepart in emotions/ association, route by which emotions can expressthe thalamus also plays a part themselves in changed bodily func-in arousal and producing com- tions. It also plays a vital role in wa-plex reflex movements. (1) ter balance, waking state, appetite,The hypothalamus consists of and body temp. (1)several structures that are un-der the thalamus. It is smallbut extremely important., be-cause it contributes to both sur- 8
The Meninges Three meninges: dura mater, Function of CSF (cerebrospinal flu-arachnoid membrane, pia mater id)(2) • Provides supportive, protectiveInflammation of meninges: cushion (2) • Reservoir of circulating fluid,meningitis (2) which is monitored by the brain toDura mater: made of strong detect changes in internal environ-white fibrous material, outside ment (2)of brain (2) Found within subarachnoid space around the brain, spinal cord & sur-Arachnoid membrane: delicate, rounding cavities, and canals of thecob like membrane, lies betweendura and pia mater(2) brain and spine. (2)Pia mater: transparent matter Spinal cordthat adheres to the outer sur-face if the brain and spinal cord, • Within spinal cavity and extendscontains blood vessels (2) from the foramen magnum to the lower border of the first lumbar ver-
The Meninges -tebrae (2)• Oval shaped cylinder that ta-pers slightly from above down-ward with bulges in cervical re-gion & lumbar region (2)Nerve Roots• Carry sensory and motor infointo spinal canal (fibers of dor-sal nerve root and central nerveroot) (2)